Sound spectrogram of the electric organ discharges of a courting male Sternopygus macrurus recorded in the field on May 1, 1970 on Moco-Moco creek, Rupununi District of Guyana. The electrical discharges are here converted to sound, and the recording is played back at normal speed. Here the male can be heard producing frequency rises and interruptions in this two minute-long segment. Discharges of the female, and of a second wave species, Apteronotus albifrons, can be heard in the background. Distant lightning discharges are audible as clicks in the background of the recording.

Recordings made by C. D. Hopkins and K. Hopkins

References:
Hopkins, C. D. (1972). Sex differences in electric signalling in an electric fish. Science 176, 1035-1037.
Hopkins, C. D. (1973). Lightning as background noise for communication among electric fish. Nature 242, 268-270.
Hopkins, C. D. (1974). Electric communication in the reproductive behavior of Sternopygus macrurus(Gymnotoidei). Z. Tierpsychol. 35, 518-535.